Kathleen L. Londry

Sorption and desorption of three endocrine disrupters in soils.

Sorption of the estrogens estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) on four soils was examined using batch equilibrium experiments with initial estrogen concentrations ranging from 10 to 1000 ng mL−1. At all concentrations, >85% of the three estrogens sorbed rapidly to a sandy soil. E1 sorbed more strongly to soil than E2 or EE2. Partial oxidation of E2 to E1 was observed in the presence of soils. Autoclaving was more effective at reducing this conversion than inhibition with sodium azide or mercuric chloride, and had little effect on sorption, relative to the chemical microbial inhibitors. Sorption of EE2 was greater for fine-textured than coarse-textured soils, but greater than 90% of EE2 sorbed onto all four soils. The greatest degree of desorption of estrogens from the sandy soil occurred with the lowest initial concentration of 10 ng mL−1 and reached levels ≥80% for E1 and E2. Desorption of EE2 was greater in coarser textured soils than finer-textured soils. Again, relative desorption from all soils was greatest with low initial concentrations. Therefore, at environmentally relevant concentrations, estrogens quickly sorb to soils, and soils have a large capacity to bind estrogens, but these endocrine-disrupting compounds can become easily desorbed and released into the aqueous phase.

Comparison of Microbial Biomass, Biodiversity, and Biogeochemistry in Three Contrasting Gold Mine Tailings Deposits

Abstract An interdisciplinary approach was used to assess the biogeochemistry of three deposits of gold mine tailings in Nopiming Provincial Park, Manitoba, Canada. Each depositional site has developed varying levels of natural revegetation over the past 70 years. Although the tailings are the products of processing similar carbonate-hosted quartz-carbonate shear zones by the same methods, the physical, chemical, and hydrogeological conditions varied among sites. The sample from the barren tailings area at the Central Manitoba site was lower in pH (4.87 ± 1.34) and higher in total sulfur (337 ± 166 μmol/g) and copper (44.5 ± 20.9 μ mol/g) than samples from the other two sites. Microbial activities have impacted the biogeochemical distribution of carbon, sulfur (total, sulfide, sulfate), and iron (total, Fe(II)) in the tailings at all three sites. The microbial communities were distributed throughout the tailings, but the biomass and biodiversity were greatest at the surface in the revegetated (Ogama-Rockland) and partially revegetated (Gunner) tailings. In contrast, the most barren set of tailings (Central Manitoba) had the greatest biomass and biodiversity in the middle layer (15 cm depth), which also had the greatest abundance of metals, anions, and carbon. The distribution of fatty acid methyl esters (FAME) in the tailings was dependent on both the depth and the individual characteristics of the site. The biomass and biodiversity correlated with the physicochemical conditions, particularly as affected by water movement and hydrology. The primary determinants limiting natural attenuation of the sites may be insufficient calcite buffering, hydrogeology, and the distribution of microbes, rather than a lack of microbes.

Endocrine Disrupting Compounds (EDC) in Municipal Wastewater Treatment: A Need for Mass Balance

Increasing attention has been focused on endocrine disrupting compounds (EDCs) as pollutants in municipal wastewater. Recent studies have shown that these compounds can have a negative impact on the environment, and that in many cases they are not efficiently removed in wastewater treatment plants (WWTPs). Studies have also revealed that their destruction and transport out into the environment depend on the design and operational characteristics of these treatment systems and on the properties of the chemicals themselves. This paper reviews the current knowledge on EDCs, natural and synthetic hormones including estrone (E1), 17β~estradiol (E2), and 17α~ethinylestradiol (EE2) in WWTP. Several key data gaps are addressed when assessing the removal of EDCs in WWTPs. First, analytical methods used by most researchers do not account for the inactive or conjugated form of the compounds, yet they can become deconjugated to active forms during treatment, leading to an additional source of contaminant load. Next, insufficient measurements are made at various stages within the WWTP preventing adequate analyses on how each unit process contributes to degradation. Currently, there is no standardized procedure for assessing degradation of EDCs in WWTPs, and it is often difficult to compare published data generated by individual test protocols. This paper identifies streams that should be sampled in WWTPs and suggests a mass balance approach that takes into account all forms of the compound in both liquid and solid phases. Issues of potential concern in performing mass balances are discussed leading to a proposal of variables that should be analyzed and included in published articles. The adoption of similar methods by researchers in future work will produce a better picture of the presence and fate of these compounds in the environment.

2,4-Dichlorophenoxy Acetic Acid Mineralization in Amended Soil

The application of municipal biosolid or liquid hog manure to agricultural soils under laboratory conditions at 20°C influenced the fate of the herbicide 2,4-D [2,4-(dichlorophenoxy)acetic acid] in soil. When 2,4-D was added to soil at agronomic rates immediately after the addition of manure or biosolids to a coarse-textured soil, the percentage of 2,4-D mineralized at 100 days was about 47% for both treatments, compared to only 31% for control soils without amendments. The enhanced 2,4-D mineralization as a result of amendment addition was due to an increased heterotrophic microbial activity, with the greatest increases in soil respiration occurring for soils amended with biosolids. When additions of 2,4-D were delayed for one, two, or four weeks after the amendments were applied, the additions of amendments generally reduced 2,4-D mineralization in soil, particularly for manure, indicating that the effect of amendments on enhancing soil microbial activities diminished over time. In contrast, the mineralization of 2,4-D in control soils was less dependent on when 2,4-D was applied in relation to pre-incubations of soil for zero, one, two, or four weeks. The effect of manure on decreasing 2,4-D mineralization in specific soils was as large as the effect of soil texture on differences in 2,4-D mineralization across soils. Because manure was not found to impact 2,4-D sorption by soil, it is possible that 2,4-D mineralization decreased because 2,4-D transformation products were strongly sorbed onto organic carbon constituents in manure-amended soils and were therefore less accessible to microorganisms. Alternatively, microorganisms were less likely to metabolize the herbicide because they preferentially consumed the type of organic carbon in manure that is a weak sorbent for 2,4-D.

In-field variation in 2,4-D mineralization in relation to sorption and soil microbial communities.

This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg−1, the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day−1 and the total amount of 2,4-D mineralized at 130 days (M130) ranged from 24 to 39%. Both k and M130 were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M130 were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.